What is the difference between model numbers beginning with the letter B or A after the first dash?
The 1/16th DIN Watlow EZ-Zone PM controllers beginning with the letter B after the first dash have blue tooth communication capability. The blue tooth is user selected on or off and there is no extra charge for this feature. Blue tooth allows viewing or programing the controller via a smart phone or blue tooth enabled pad using Watlow's EZ-Link software available free from Apple's app/store or the Google/play store. The 1/16th DIN Watlow EZ-Zone PM controllers beginning with the letter A after the first dash have standard serial bus capability allowing RS-485 2-wire to USB communication using the same Watlow EZ-Link free software together with a serial to USB accessory connector purchased seperatly.